One of the most frequently asked questions I receive from readers is for information on the publication dates of various articles on the website. While I'm always happy to answer these requests, you can properly cite an online article in APA format without knowing the publication date of the material.
According to the official APA style website, the correct way to do this is to include the notation "n.d." for no date. For example, you would cite an article from this website as follows:
Cherry, K. (n.d.). How to become a psychologist. About.com. Retrieved from http://psychology.about.com/od/careersinpsychology/ss/become-a-psychologist.htm
Learn more by checking out some of these examples of APA format.
Reference:American Psychological Association. (2010). How do you cite website material that has no author, no year, and no page numbers? Retrieved from http://www.apastyle.org/learn/faqs/cite-website-material.aspx